1. Field of the Invention
The present invention relates to an integrated circuit having a logic gate block functioning in accordance with circuits defined in the interior thereof and data, or a gate array for applying wirings to a master slice in accordance with the application, and more particularly to an integrated circuit and a gate array improved in efficiency of design of an analog-digital composite electronic circuits.
2. Description of the Prior Art
There has heretofore been widely used a programmable logic device (hereinafter referred to as a "PLD") which is an integrated circuit formed to realize an optional logic circuit near at hand of a user. The PLD of various types are provided for the users.
The application in the interior of the above-described PLD is performed such that various memory elements and various logic elements are selectively connected to one another. As the means (elements) used for programming a logic circuit, N-MOS transistors and P-MOS transistors are used as switching elements. The means selectively connected to one another for programming the logic circuit will hereafter be referred to as Switching Station (S/S) elements.
Applying the integrated circuits to electronic machines and components leads to the many advantages of not only rendering the whole sizes of the electronic machines and components compact but also improved reliability of the electronic machines and components, lowered electric power consumption and so forth. Accordingly, many users utilize the above-described PLD to facilitate the circuit designing of the integrated circuit for widely applying the integrated circuits to the electronic machines and components. Along with this trend, various electronic circuits of the electronic machines and components are selected as the targets for developing and providing the PLD of various types.
In recent years, the digital circuit technique has achieved a great advancement in the respects of the improvement in mounting density of logic devices and the improvement in signal processing speeds. Along with this trend, the electronic circuits and the electronic circuit devices, which have heretofore been using the analog circuit technique, are formed by the digital circuit technique, so that not only the electronic circuits and the electronic circuit devices are rendered compact in size and the electric power consumption is decreased as described above, but also the number of the electronic parts being used can be reduced and the number of corrected portions such as the trimmer can be decreased, thus improving the manufacturing efficiency and improving the reliability of the whole electronic circuits.
Further, it has been realized as a result of the advancement of the size-reducing technique of the integrated circuits that a digital circuit obtained by digitalizing an analogue circuit and a concerned analog circuit formed together with the digital circuit can be formed on one and the same integrated circuit. As the methods of realizing the integrated circuit formed of the above-described analog-digital composite electronic circuit, the following forming methods have been proposed.
1. An integrated circuit (a building-block type standard cell) in which a logical circuit (digital circuit), a memory and an analog circuit are formed to provide macrocells, respectively, and these macrocells are integrated on one chip.
2. An integrated circuit (a multichip-module) in which a logic circuit (digital circuit), a memory and an analog circuit are formed to provide integrated circuit chips independently of one another, and these plurality of integrated circuit chips are mounted onto a polyimide pattern or a silicone substrate having programmable wiring.
3. An integrated circuit (a waferscale integration) in which a system consisting of a logic circuit (a digital circuit), a memory and an analog circuit is integrated on the whole surface of a wafer.
However, the integrated circuit in which an analog-digital composite electronic circuit is integrated on one chip as described above presents the problem that a very long time is required for developing such an integrated circuit as described above, the problem that an enormous cost of development is required, and so forth.
Since the analog signal is the signal having the meaning in the continuously varied value itself (of voltage and current), in controlling this analog signal, a digital signal having the bit number far more than the bit number for a mere on-off control. Accordingly, in the integrated circuit in which the analog-digital composite electronic circuit is integrated on one chip, such a problem is presented that the number of the wirings of the digital signals for controlling the analog signals becomes very large.